Chinese authorities have accused a top GlaxoSmithKline executive of ordering employees to commit bribery, following a 10-month probe into the embattled British drugmaker.

Police in the central Chinese city of Changsha said that Mark Reilly, GSK's former head of China operations, had "pressed his sales teams to bribe hospitals, doctors and health institutions" in order to gain billions of dollars in illegal revenue, the official Xinhua news agency reported.

Mr Reilly and two other GSK executives, Zhang Guowei and Zhao Hongyan, also allegedly bribed Chinese government officials in Beijing and Shanghai, it said.

Changsha police have handed the case over to prosecutors.

A Shanghai-based GSK spokeswoman did not immediately respond to a request for comment.

Last June, Chinese authorities detained four Chinese GSK executives on allegations that employees used nearly $500 million in bribes to boost sales.

Mr Reilly, a British national, had left China days after the detentions and investigation were announced.

But he returned within weeks in order to "help further with the investigation", GSK said in a statement at the time, and has reportedly been barred from leaving the country since.

Police said that company staff had offered bribes to officials and doctors, with physicians allegedly earning a seven to 10 per cent cut from sales of GSK drugs they prescribed, Xinhua previously reported.

GSK staff were also suspected of taking kickbacks from travel agencies to organise conferences, some of which were fake.

Mr Reilly and other GSK executives "tried every effort to cover the illegal sale practice during regular checks by regulatory authorities", Changsha police said, according to Xinhua.

China's healthcare sector is widely considered to be riddled with graft, given the opaque tendering system for drugs and doctors' low salaries.

The inquiry was launched at a time when China initiated sweeping probes into alleged malpractice by foreign firms in various sectors, and against the backdrop of an anti-graft campaign backed by President Xi Jinping to root out official corruption.

A total of 46 suspects are involved in the case, Xinhua said, and dozens of GSK's local employees have been arrested.